Is a person held accountable for merely thinking about and imagining scenarios of violence, killing, and wars, if that is purely for enjoyment and to pass the time?

There is no blame in imagining probable future events, according to the hadith: "Indeed, Allah has pardoned my Ummah for whatever they whisper to themselves, as long as they do not act upon it or speak of it." However, it is more befitting to direct one's mind and concerns towards beneficial actions, such as acquiring useful knowledge and striving to reform the Ummah by inviting people to Allah, connecting them with Him, improving their conditions, and supplicating for their guidance and cooperation in good. This is more worthy than mere unproductive imaginings that waste time.